Author Topic: SNES PINOUTS & PROTOCOL  (Read 475 times)

netfreak

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SNES PINOUTS & PROTOCOL
« on: February 18, 2017, 04:43:57 pm »
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            SUPER NINTENDO ENTERTAINMENT SYSTEM: PINOUTS & PROTOCOL
                                       
   Contents:
   
     * Chapter 1) About the Author
     * Chapter 2) Introduction
     * Chapter 3) SNES Multi-out cable connector pins.
     * Chapter 4) SNES Controller cable connector pins.
     * Chapter 5) SNES Controller Communication Protocol
     * Chapter 6) SNES Controller Button-to-Clock Pulse Assignment
       
   
   [Document Version: 1.01] [Last Updated: 3/26/96]
   
   
     _________________________________________________________________
   
   
   
                         CHAPTER 1) ABOUT THE AUTHOR
                                       
   Author: Jim Christy
   Version: 1.01
   E-Mail: jchristy@hplred.HP.COM
   
   
     _________________________________________________________________
   
   
   
                           CHAPTER 2) INTRODUCTION
                                       
   For all you game hardware enthusiasts out there, I took the
   opportunity this weekend to put a scope on my Super Nintendo
   connectors and find out what is going on. Because the standard
   Multi-out cable connector only has internal contacts for the audio and
   video signals, I had to find some more push-in gold contacts at a
   local store to fully break out all the signals. It appears easier to
   do this than make your own connector.
   
   In short, I found that in addition to S-VHS, the multiout also
   supports RGB and sync. I also got the controller pinouts and protocol,
   which opens up some interesting possibilities. One could rather easily
   construct a "macro recorder" that records your exact button presses
   for a game sequence and allows you to play them back. They will be
   time-accurate by definition of the protocol, and depending on how
   random the game plays, you should be able to replay those sequences
   that get boring, and then take over control when you want.
   
   If all of this is already well known, then sorry for the waste of net
   bandwidth...
   
   
     _________________________________________________________________
   
   
   
               CHAPTER 3) SNES MULTI-OUT CABLE CONNECTOR PINS.
                                       
   These are numbered the way Nintendo did, and the view is looking back
   "into" the connector on the CABLE.
   

        1       3       5       7       9      11

        |       |       |       |       |       |
        |       |       |   _   |       |       |
       --------------------/ \--------------------
     /                                             \
    |                                               |
    |                                               |
     \                                             /
       -------------------------------------------
        |       |       |       |       |       |
        |       |       |       |       |       |

        2       4       6       8      10      12



        Pin     Description
        ===     ===========
        1       Red analog video out   (1v DC offset, 1vpp video into 75 ohms)
        2       Green analog video out (1v DC offset, 1vpp video into 75 ohms)
        3       Composite H/V sync out (1vpp into 75 ohms)
        4       Blue analog video out  (1v DC offset, 1vpp video into 75 ohms)
        5       Ground
        6       Ground
        7       Y (luminance) signal for S-VHS (1vpp into 75 ohms)
        8       C (chroma)    signal for S-VHS (1vpp into 75 ohms)
        9       NTSC composite video signal (1vpp into 75 ohms)
        10      +5v (Could be just a high logic signal)
        11      Left channel audio out
        12      Right channel audio out

   
   Additional Notes:
   
   As seen above, the SNES does have RGB capability. I was able to get a
   stable raster on my NEC MultiSync "classic" using the RGB and sync
   pins. However, the video levels are not RS-170 compatible. The DC
   offset needs to be filtered out with some large capacitors and the
   peak-to-peak video amplitude may need to be reduced to 0.7v by using a
   lower load impedance than 75 ohms. The Y/C (S-VHS) signals *appear* to
   be directly usable, but tests cannot be made until I find the pinouts
   for the S-VHS connector on my TV.
   
   
     _________________________________________________________________
   
   
   
               CHAPTER 4) SNES CONTROLLER CABLE CONNECTOR PINS.
                                       
   I could not find a Nintendo numbering scheme, so I made one up. The
   view is looking back "into" the connector on the CABLE.
   

       ----------------------------- ---------------------
      |                             |                      \
      | (1)     (2)     (3)     (4) |   (5)     (6)     (7) |
      |                             |                      /
       ----------------------------- ---------------------


        Pin     Description             Color of wire in cable
        ===     ===========             ======================
        1       +5v                     White
        2       Data clock              Yellow
        3       Data latch              Orange
        4       Serial data             Red
        5       ?                       no wire
        6       ?                       no wire
        7       Ground                  Brown

   
   Additional notes:
   
   Pins 5 and 6 show a DC voltage of 5v on a DMM. I forgot to look at
   them on a scope so there may pulses too. However, they don't connect
   to anything at present.
   
   The controllers have a small circuit board with 2 surface mount 14-pin
   ICs, marked by Nintendo as IC-A and IC-B. Although rubber domes are
   used to provide the tactile response of the buttons, they are not
   capacitive technology as originally thought. Instead they use what
   appears to be carbon impregnated rubber on the underside which makes a
   resistive path (200 ohms) across 2 carbon coated PCB pads when
   depressed.
   
     * The red wire goes to pin 2 on IC-A.
     * The orange wire goes to pin 8 on both IC-A and IC-B.
     * The yellow wire goes to pin 9 on both IC-A and IC-B.
       
   
   IC-A and IC-B appear to be identical, with a 91 date code and have
   another (possible part number) of 545. These are most likely 2
   parallel load shift registers in series. Buttons on the controller
   pull the parallel load inputs to ground through the contact formed by
   pressing a button. IC-B serially feeds IC-A, which then drives the
   serial data line to the SNES CPU.
   
   
     _________________________________________________________________
   
   
   
              CHAPTER 5) SNES CONTROLLER COMMUNICATION PROTOCOL
                                       
   Every 16.67ms (or about 60Hz), the SNES CPU sends out a 12us wide,
   positive going data latch pulse on pin 3. This instructs the ICs in
   the controller to latch the state of all buttons internally. Six
   microsenconds after the fall of the data latch pulse, the CPU sends
   out 16 data clock pulses on pin 2. These are 50% duty cycle with 12us
   per full cycle. The controllers serially shift the latched button
   states out pin 4 on every rising edge of the clock, and the CPU
   samples the data on every falling edge.
   
   Each button on the controller is assigned a specific id which
   corresponds to the clock cycle during which that button's state will
   be reported. The table in section 4.0 lists the ids for all buttons.
   Note that multiple buttons may be depressed at any given moment. Also
   note that a logic "high" on the serial data line means the button is
   NOT depressed.
   
   At the end of the 16 cycle sequence, the serial data line is driven
   low until the next data latch pulse. The only slight deviation from
   this protocol is apparent in the first clock cycle. Because the clock
   is normally high, the first transition it makes after latch signal is
   a high-to-low transition. Since data for the first button (B in this
   case) will be latched on this transition, it's data must actually be
   driven earlier. The SNES controllers drive data for the first button
   at the falling edge of latch. Data for all other buttons is driven at
   the rising edge of clock. Hopefully the following timing diagram will
   serve to illustrate this. Only 4 of the 16 clock cycles are shown for
   brevity.
   

                           |<------------16.67ms------------>|

                           12us
                        -->|   |<--

                            ---                               ---
                           |   |                             |   |
        Data Latch      ---     -----------------/ /----------    --------...


        Data Clock      ----------   -   -   -  -/ /----------------   -  ...
                                  | | | | | | | |                   | | | |
                                   -   -   -   -                     -   -
                                   1   2   3   4                     1   2

        Serial Data         ----     ---     ----/ /           ---
                           |    |   |   |   |                 |
        (Buttons B      ---      ---     ---        ----------
        & Select        norm      B      SEL           norm
        pressed).       low                            low
                                12us
                             -->|   |<--

   
   
     _________________________________________________________________
   
   
   
         CHAPTER 6) SNES CONTROLLER BUTTON-TO-CLOCK PULSE ASSIGNMENT
                                       
   

        Clock Cycle     Button Reported
        ===========     ===============
        1               B
        2               Y
        3               Select
        4               Start
        5               Up on joypad
        6               Down on joypad
        7               Left on joypad
        8               Right on joypad
        9               A
        10              X
        11              L
        12              R
        13              none (always high)
        14              none (always high)
        15              none (always high)
        16              none (always high)

   
   Additional notes:
   
   Clock cycles 13-16 are essentially unused. It would be interesting to
   see how the SNES responds if we drive low button data during these
   cycles. Nintendo may use these for future controllers with more
   capabilities.
   
   (From the Editor)
   
   NOTE: S-VHS is not means to mean Super-VHS. It stands for Super-Video
   (connector and output)
   
   #### Additional Info (From Kevin Horton)
   
   OK, the SNES uses the 65816 processor, which is basically a 16-bit
   version of the 6502. It runs at 3.579545 MHz (color-burst), and has an
   8-bit data bus. It can address up to 16MB.
   
   The carts are nothing more than ROM. To tell you how much data is one,
   take the number of 'MegaBits' and divide by 8 to get megabytes. That's
   how much data is really in the carts. So, an 8-mbit cart really is
   only 1 megabyte.
   

https://cdn.preterhuman.net/texts/gaming_and_diversion/Video_and_Computer_Games/SNESPin.txt